In Long-Term Evolution (LTE) networks, a base station (e.g., an e-NodeB) is implemented based on proprietary purpose-built hardware, which hinders adaptation of such networks to fast changing network conditions, demands, services, etc. Recently, as part of a trend for moving toward virtualization of network functions for a Radio Access Network (RAN) in order to address the above-mentioned shortcomings, base band units (BBU) of such e-NodeBs are virtualized and implemented on a cloud environment (as one of Virtualized Network Function (VNF) use cases run over commercial off-the-shelf (COTS) servers). In such a trend, flexibility and controllability are important to fully exploit the advantage of the given cloud environment.
However, a vBBU according to the state of the art keeps a tightly-coupled radio and backhaul protocol stacks, which makes it difficult to provide a truly flexible and controllable path between radio and backhaul (or edge cloud) parts of the vBBU in the cloud environment. For example, in a distributed cloud with distributed evolved packet cores (EPCs), the vBBU of each e-NodeB needs to be connected to (or shared by) different physical/logical backhaul links to the EPCs (or edge clouds).
Moreover, due to a processing time requirement, Layer 2 (L2) and Layer 3 (L3) processing are virtualized over general purpose processors (GPP) while Layer 1 (L1) radio communications are run over special hardware, e.g., a graphical processor unit (GPU) array.
While the above described schemes that are currently available, provides better flexibility compared to hardware proprietary purpose-built e-NodeBs, the embedding of backhaul protocol stacks inside vBBUs prevents flexible mapping between radio and backhaul resources and backhaul resources to truly scale independent of radio protocol stacks (i.e., the number of backhaul protocol stacks scales with the number of vBBUs). In other words, the current design of vBBUs does not allow customized VNFs to be added inside eNBs, especially between the radio and backhaul protocol stacks.